JavaScript #2

Haebin Ethan Jeong·2020년 7월 21일
0

String and Number

console.log("200"-"hello"); will return NaN.

How to convert from String to Number.

  • Using Number function
var birthYearInput = "2000";
console.log(typeof birthYearInput);
>> string

var numberBirthYear = Number(birthYearInput);
console.log(typeof numberBirthYear);
>> number
  • Using parseInt, parseFloat
parseInt("1.901");
parseFloat("1.901");
  • Using - 0
var numberAsNumber = "1234"; 
var numberAsString = numberAsNumber - 0;

How to convert from Number to String

  • Using .toString()
var numberAsNumber = 1234; 
var numberAsString = numberAsNumber.toString();
  • Using + ""
var numberAsNumber = 1234; 
var numberAsString = 1234 + "";

Date and Time

var rightNow = new Date();
console.log(rightNow);

>>2020-07-21T04:38:26.937Z

How to get more specific times

let rightNow = new Date();
let year = rightNow.getFullYear();
let month = rightNow.getMonth()+1;
let date = rightNow.getDate();
let day = rightNow.getDay();
let currentHour = rightNow.getHours();
let currentMin = rightNow.getMinutes();

Getting time in miliseconds

let rightNow = new Date();
let time = rightNow.getTime();

>> 1595306409520

Generating a whole random number

function getRandomNumber (min, max) {
  let randomnumber = Math.floor(Math.random() * (max - min + 1)) + min;
  return randomnumber;
}
  1. When we use Math.random(), it generates a random decimal random number like 0.8060133565188234 and 0.15913631950148144.
  2. We need to multiply this random number by the range of the number. In order to do so, we do Math.random()*(max - min + 1). This will generate numbers like 8.060133565188234 or 1.5913631950148144 based on the result above.
  3. In order to make the number above an integer, we do Math.floor(Math.random()*(max - min + 1))
  4. The number above is rounded down! So we need to add min. Like this. Math.floor(Math.random() * (max - min + 1)) + min
profile
I'm a Junior studying Economics and Computer Science at Vanderbilt University.

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